The invention is generally related to automotive safety restraint systems and in particular to a restraint system having a seat belt retractor driven by a reversible electric motor for securing, in a comfortable manner, a safety belt about a vehicle occupant. Current three-point safety restraint systems employ a spring biased retractor that may or may not use mechanical tension eliminators.
As is often the case, these devices maintain a constant, sometimes objectionable pressure on the occupant's shoulder. The result of this uncomfortable pressure may cause the occupant not to use the safety restraint system at all or to adjust the shoulder belt portion in a manner that creates an unsafe situation. As an example the occupant may cause the tension eliminator to engage at a position leaving a greater than optimal slack in the shoulder belt.
Commonly owned U.S. Pat. No. 4,655,311 illustrates a motor-driven seat belt system designed to eliminate excess slack in the safety belt so as to properly restrain an occupant of the vehicle during a crash. The present invention improves upon the teachings of this patent and while retaining the concept of properly protecting the occupant during a crash further enhances occupant comfort.
It is an object of the present invention to provide an electrically operable seat belt system responsive to the relative motion of the D-ring to control the tension in the safety belt. A further object of the present invention is to automatically stow the safety belt during intervals of non-use. Another object of the present invention is to properly adjust the safety belt about the occupant for maximum protection. Another object of the present invention is to lock the safety belt during a crash by physically inhibiting the rotation of the motor and thereby preventing extension of the safety belt.
Accordingly, the present invention comprises: a safety restraint system for a vehicle comprising: a safety belt attachable at one portion thereof to a buckle means. The buckle means comprising a tongue portion attached to a safety belt, and a buckle portion for receiving the tongue. A first sensor means, is provided, for generating a first signal indicative of a buckled and an unbuckled state. The system includes D-ring means adapted to be rotatably mounted to a vehicle member, for slideably receiving a shoulder belt portion of the safety belt, and second sensor means, coacting with the D-ring means for generating a second signal indicative of D-ring motion; and retractor means adapted to be secured to a structure member of the vehicle, including a take-up spool, attached to an end of the shoulder belt and a reversible electric motor, in driving engagement with the take-up spool for rotating same in rewind and reverse directions in response to rewind and reverse control signals. The system additionally includes third means for generating a third signal indicative of motor torque; and control logic means for generating the rewind and reverse control in response to the states of the first and second sensor means including first storage means, responsive to the second signal, for storing a value indicative of D-ring position. The system will automatically enter various modes of operation to stow the safety belt upon occupant exit from the vehicle and to automatically tighten the safety belt about the occupant in a controlled manner to insure occupant safety belt comfort. To control occupant comfort, the belt after being pulled taut about the occupant, is released a small amount to reduce belt tension on the occupant's shoulder to a nominal amount. The above is accomplished by monitoring D-ring position and provides safety belt tension control when the occupant moves to new temporary and/or permanent seating positions. The system also includes a crash mode which monitors the output of a sensor, that responds to vehicle deceleration. Upon sensing a high deceleration level the retractor motor is commanded to immediately rewind to eliminate all safety belt slack. A retractor lock solenoid is also provided to physically lock the retractor to prevent the paying out of the safety belt during high decleration conditions.